Three unrelated products are sold as “high temperature grease,” and they fail in different ways when swapped for one another. Picking correctly starts with deciding what the grease is actually there to do — lubricate motion, seal a static joint, or move heat across one.
One Name, Three Functions
The term describes a temperature capability, not a job. Separating the three before comparing data sheets prevents the most common and most expensive specification error in this category:
| Function | What the grease is for | Specified by |
|---|---|---|
| Mechanical lubrication | Maintaining a load-bearing film between moving metal surfaces | Dropping point, thickener chemistry, base-oil volatility, EP additives |
| Sealing and vacuum service | Sealing a static joint and preventing seizing — not lubricating motion | Volatility, chemical inertness, consistency, temperature range |
| Thermal transfer | Conducting heat across an air-gapped interface — not reducing friction | Thermal conductivity, electrical behaviour, non-drying stability |
Incure manufactures the second and third. Rotating-equipment bearing lubrication is a distinct product class that Incure does not supply; if that is the requirement, specify a dedicated bearing grease against its dropping point (ASTM D2265) and evaporation-loss data (ASTM D2595), and treat continuous service temperature rather than peak excursion as the governing figure.
Q: Which high temperature grease does a given joint need?
A: Ask whether anything moves, and whether heat has to cross the joint. If metal slides or rolls against metal under load, the requirement is a bearing lubricant. If the joint is static and the goal is to seal it, exclude contamination, and keep it from seizing so it can be opened again later, the requirement is a sealing grease — load-carrying capacity is irrelevant and low volatility is what matters. If the joint is static and the goal is to get heat out of a component into a heat sink, the requirement is a thermal interface grease, where thermal conductivity and electrical behaviour decide the grade and lubricity plays no part at all.
The distinction is not academic. A thermal grease on a bearing has no load-carrying film and the bearing fails. A bearing grease on a vacuum flange outgasses into the chamber, so base pressure never stabilises. A sealing grease at a heat-sink interface conducts heat poorly and the component runs hot. Each substitution looks harmless at assembly and shows up later as a failure that gets blamed on the wrong part.
Sealing and Vacuum Duty: Pyra-Sil™ 802
Incure’s Pyra-Sil™ 802 high vacuum silicone grease is built for static sealing across a wide thermal range, rated from −45°C to 204°C. Low volatility is its defining property: an ordinary hydrocarbon grease contains components that evaporate under reduced pressure and vent into the system they were meant to seal, which is why a mechanically similar general-purpose grease is a genuine risk in vacuum service rather than a minor compromise.
Its thixotropic gel consistency keeps it on the flange face or O-ring instead of migrating or dripping under gravity — as important on a joint that sits untouched for years as during application. It is chemically inert, oxidation resistant, translucent for visual inspection, and functions as an electrical insulator where the joint sits near a live connection. Typical duty covers O-ring and gasket lubrication on seals that are repeatedly opened and reseated, vacuum flange sealing, valve and stopcock lubrication on ground-glass laboratory joints, cryogenic fitting seals that must stay pliable at the cold end of the range, and chemical process equipment where oxidation resistance and low volatility are needed together.
Thermal Transfer Duty: Epo-Weld™ TCG Grades
Incure’s Epo-Weld™ thermally conductive grease line exists to eliminate the air gap between two mating surfaces so heat crosses the interface instead of stalling at it. The selection decision is electrical, not mechanical, because the three grades share essentially the same thixotropic paste consistency:
- TCG-10 is alumina-filled: thermally conductive while remaining electrically insulating, which is what makes it appropriate for mounting transistors and rectifiers where the interface sits near live circuitry and must not become a leakage path. It holds stable, non-drying performance up to 550°F.
- TCG-30 is aluminium-filled and conducts both heat and current, suited to grounding connections and high-power electrical contacts at moderate cost.
- TCG-40 is copper-filled, delivering lower contact resistance than aluminium, for high-current switches and grounding lugs where voltage drop across the joint is a primary design concern.
None of the three cure into a rigid bond, so any of these interfaces can be dismantled and cleaned without the joint-preparation work a cured adhesive demands. Where the thermal joint should instead be permanent and structural, Incure’s thermally conductive epoxy line covers that case.
Email Us with the joint’s function — sealing, thermal transfer, or both — along with its service temperature and whether electrical isolation is required, and Incure’s engineers can confirm the grade.
Why “Non-Drying” Is the Specification That Decides Service Life
For both sealing and thermal duty, the figure that predicts long-term behaviour is not the headline temperature rating but whether the grease stays a grease. A formulation that hardens, crumbles, or bleeds its carrier reintroduces exactly the air gap or leak path it was applied to close. The interface that measures correctly at assembly and quietly loses most of its performance eight months later is almost always this failure, not a wrong conductivity or volatility number at the outset.
That makes two checks worth building into maintenance rather than relying on the data sheet alone: inspect a representative joint after its first sustained thermal cycling period and confirm the grease is still pliable and still fully covering the mating face, and re-verify after any change of grade or supplier. On thermal interfaces, measure component temperature with a contact sensor rather than inferring performance from the grease’s rated conductivity, since the actual bond-line thickness and surface flatness influence the result as much as the material does.
Matching function first, then temperature range, then electrical requirement is what makes a high temperature grease deliver its rated service life. Contact Our Team to confirm a grade for your sealing or thermal-interface application.
Visit www.incurelab.com for more information.